In many fields of technology it is necessary to protect fastening elements, such as rivets, bolts or screws, which couple two components to each other, against damage by corrosion and other environmental influences. This applies in particular to the portion or portions of the fastening element projecting from the surface. For example, in aircraft manufacturing structural components of an aircraft are typically interconnected by rivets, wherein portions of the rivets project from the combined surface of the structural components.
It is common practice to apply or re-apply a protective coating to any projecting portions of a fastening element, and preferably also to the surrounding area of the surface from which the fastening element is projecting, after the fastening element has been put in place to secure to components to each other. Corresponding processes have to take into consideration that the projecting portions may have very different shapes and dimensions and that they may have complex geometries, such as undercuts.
One known process for applying a protective coating to projecting portions of fastening elements is by manually using a brush in order to apply a liquid coating material to the projecting portions and the surrounding surfaces. While this approach allows in principle for a reliable application of coating material, it is time consuming and involves a high workload under often poor ergonomic conditions.
A further known process utilizes an airbrush for applying liquid coating material. As is typical for methods employing an airbrush, the process requires safety measures, such as a suction and/or filtration mechanism and protective suits or masks, for protecting workers and surrounding areas from coating material aerosol. These safety measures have an impact on the overall energy consumption and on the ergonomics of the process.
Applying a protective coating by an immersion bath is not possible for large components, and it is technically challenging to achieve a constant coating material thickness and to limit the amount of coating material to the amount necessary to protect the fastening elements.